Electron-discharge device



Aug. 4, 1925.

, 1,548,757 J. SCOTT-TAGGART ELECTRON DISCHARGE DEVICE Filed Nov. 30, 1920' 2 Sheeis-Sheet 1 Aug. 4-, 1925. 1,548,757

J. SCO.1T-TAGGARI ELECTRONDISCHARGE DEVICE Filed Nov, 30, 1920 2 Sheets-Sheet 2 IQ 6, L =5 fl Z l L Z: [cl-cal! 6/] T 314120414 50? 6157a}? fifazf-ijzyari ethane/15 Patented Aug. 4, 1925.

1,548,757 PATENT OFFICE.

UNITED STATES JOHN SCOTT-TAGGABT, OF LONDON, ENGLAND, ASSIGNOR TO COMMERCIAL CABLE COMPANY, OF NEW YORK, N. Y.

ELECTRON-DISCHARGE DEVICE.

Application filed November 80, 1920. Serla1 No. 427,410.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L., 1318.)

To all whom it may concern:

Be it known that I, J OHN SCOTT-TAGGART, a subject of the King of Great Britain, residing in London, England, have invented certain new and useful Improvements in Electron-Discharge Devices (for which I have filed applications in England, dated 17 Sept, 1919, Serial No. 22,863, Patent No. 166,260, and dated 5th Nov., 1920, Serial No. 31,376, Patent No. 179,568), of which the following is a specification.

This invention relates to electron discharge devices or thermionic valves es ecially for use in wireless signalling, and as for its object to enable such devices to be applied as substitutes for negative resistances or for amplification or for other purposes in the art of wireless communication.

It is well known that in ordinary electron discharge devices or valves an increase in the positive potential of the anode with respect to the cathode causes an increase in the anode current, also known as a space current. According to the present invention an opposite effect is obtained with a single valve or electron discharge device having two or more anodes, by a redistribution of the electrons passing from the, cathode to the anodes which does not depend upon the liberation of secondary electrons on one of the anodes, but upon the diversion to one of the anodes of electrons emitted by the cathode, that is, space current, which would otherwise pass to the other anode or anodes and the consequent reduction of current from the cathode to the first anode.

This redistribution ofelectron current may be consequent upon a variation of potential of a control electrode or grid or of one of the anodes which are so disposed and connected with respect to each other and the othe elements of the valve as to efiect the result described.

For a better understanding of the operative principle of the device which will be hereinafter identified as a negatron valve or negatron, reference is made to the accompanying drawings wherein Fig. 1 is 21. diagrammatic view of one form ofv the device; Fig. 2 a similar view embodying a modification; Figs. 3 and 4 are diagrams illustrating the application of the invention to amplifying purposes; Fig. 5 is a diagram illustrating its use to provide a circuit having a falling voltage-current characteristic, that is, a circuit wherein an increase in voltage produces a decrease in current, and vice gersai Figs. 6 and 7 show modifications of In Fig. 1 the two anodes A, B, which for convenience of reference will be called the A anode and the B anode respectively, are in the form of flat plates-arranged parallel with each other on opposite sides of an electron-emitting cathode such as a filament F heated to incandescence and of a control electrode or grid G, all'being con tained in an evacuated vessel, e. g. an evacuated glass bulb. Batteries C, D, E are connected with the various elements as v shown. The battery E gives the id G a suitable operating potential, re erably negative with respect to the catho e F. The batteries 0 and D are so connected with the anodes and cathodes as to make the anodes positive with respect to the cathode and so cause a flow of electrons through the evacuated space from the cathode to the respective anodes. Batteries C, D and E are of course chosen of proper voltages to cooperate with the characteristics of the vacuum tube, and are preferably adjustable in this respect, as is usual in apparatus of this nature and as shown in the various fig ures. These electron currents will be referred to as the A anode current and the B I anode current respectively. The grid G is connected to the anode A by a circuit including a battery E, preferably adjustable as shown in Fig. 1, so as to impress any desired potential on the grid.

If we assume that the electrode G is given by means of variable source E a potential sufficiently negative to that of the cathode 99 F to reduce the B anode current to a low value, there will be a steady A anode current whose magnitude is determined by the operating characteristics of the cathode, and the difference of potential applied between 100 cathode F and anode A, in other words by the normal impedance of this combination of cathode and anode. By normal impedance is meant the impedance existing bet-ween an anode at a normal operating potential and the cathode at a normal operating tem-- perature, when said two factors alone serve to determine the value of the impedance;

that is, if there be an interposed grid, when said grid has no bias such as would chan e the value of the electron flow. If now t e existing positive potential of A with res ect to the cathode F is increased, there w 1l be a corresponding increase in the potentlal of G with respect to F, that is, G Wlll become less negative to the cathode F. Gonseuently a larger B anode current begins to ow, and assuming that the cathode F be operated so as to provide a saturation condltion, some of the electrons which normally would flow from F to A are diverted to B, and the normal A anode current is correspondingl reduced, instead of mcreasmg as it wou d if the elements F and A alone were present, upon increase of the potential of A. The circuit ACF thus ossesses a fallin volta e-current characteristic which may be uti ized to ofiset or neutral ze wholly or partially the resistance of a circuit inserted in the ACF circuit, that is, the

current in such circuit may be made larger for a given ap lied volta e than it would be without the ai of the A F circuit.

The diminution of A anode current due to diversion of electrons to the B anode may more than counteract the normal increase of A anode current due to increase of A anode potential, in which case the device acts as stated above, or the diversion eifect may be the less in value, in which case the device would act as an ordinary resistance, or the two efiects could be made to balance each other so that the A anode current would not be affected b any variation of the potential of A wit in certain limits. The diversion effect of the control electrode G may be varied in a number of ways, by altering the operating conditions, for exam le the filament temperature, or suitably modifying the relative positions of the electrodes.

If it is desired to overcome the resistance in a conducting circuit it is only necessary to connect such a circuit in the A anode circuit. By connecting an external resistance circuit in series with the A anode circuit and making the resistance such that. the rising voltage-current characteristic due thereto is nearly offset by the fallin voltage current characteristic of the A F circuit,

I the device will act as a very efiicient voltage amplifier. If the external resistance be connected in parallel with the A anode circuit, for instance to A and F, the device will act as a current magnifier.

It is to be noted that the device operates entirely on the principle of the diversion to a B anode or anodes of electrons, that is, space current, which would otherwise pass to the anode A. The same effect could not be lproduced b the use of two valves.

t may be esirable to use one battery in place of the two batteries 0 and D. It may also be desirable to include an adjustable resistance between the battery supplying a positive potential to A and the anode A itself.

A suitable wireless receiving circuit ma be arranged by placing the receiving osci latory circuit 1n series with the A anode circuit of the negatron. In addition, a pair of telephones shunted by a variable condenser may be included in series with the circuit, as shown in Fi 6.

Another useful circuit is obtained by taking the leads from the positive side of C and the anode A and connecting them across the control electrode and cathode of a simple three-electrode device wireless receiving circuit. This neutralizes losses in the control electrode circuit of the three-electrode device. This is illustrated in F i 7.

In the above description, by t re A anode circuit is normally meant the external path taken by current corresponding to electrons going to the A anode. Similarly, by B anode circuit is meant the external path taken by current corresponding to electrons going to the B anode.

In the arrangement shown in Fig. 2 the negatron valve contains two anodes A and B respectively arranged on opposite sides of the cathode filament F. A control electrode G is suitably placed to control the electron current flowing from F to B. The A anode circuit includes an indicator I and a battery C and the B anode circuit includes a battery D.

The electron current from the filament F distributes itself over the divided paths available, and the temperature of the filament is adjusted so as to make the total electron emission from the filament approximately that corresponding to a saturation condition and which is e ual to the sum of the electron currents in t e two anode circuits. Under these conditions an increase of potential of the electrode G with respect to the cathode F (that is, making the electrode G less negative or more positive) will produce a decrease of current in the A anode circuit and an increase in the B anode circuit. The negatron valve therefore acts to produce a decrease of current to one of the anodes which is not due to absorption of electrons by the control electrode or grid G, but to the diversion of current to the other anode.

Such a valve may be applied to the production of various effects. F ig. 3 shows an arrangement of circuits in WhlCh the valve is used as an amplifier. A common batter C for the two anode circuits is shown, a though separate anode batteries can be used as in Fig. 2. The A anode circuit includes also an indicatorI and a resistance R. The potential of the grid G may be given a suitable value by means of a battery E or equivthe A anode current will decrease,

alent' device. Terminals J, H are indicated for the connection of the input circuit which is preferably conductive.

If the input E. M. F. increases the potential of grid G with respect to the cathogetfi, an e change of current in theresistance R communicates an added positive potential to the grid G, reinforcing the original applied potential. The added positive potentlal above mentioned is produced as follows: When a current i is flowing through B there is a potential drop, 71 between the ends of said resistance, the end remote from the positive the negatron as an am pole of battery C being atthe lower potential. If 2' decreases, the product i also decreases, that is, the drop is less, or the potential of the remote end of It rises. Inasmuch as this end is connected (throu h battery E) to the grid G, the said grid will also acquire an added positive potential. Large changes of current, as indicated by the measuring device I, can thus be obtained in the A anode circuit.

If the constants of the several circuits be suitably selected the device may be employed as a relay.

In the modified arrangement for using lifier illustrated in Fig. 4, a resistance R 18 included in the A.

anode circuit and a resistance R in the B anode circuit. If a potential positive with respect to the cathode be applied to the control electrode G, the B anode current will increase, thus making the lower end (as shown in the diagram) of the resistance R more negative because of the increased drop of potential due to the greater current through resistance R. current will decrease, similarly, making the upper end of resistance R more posltive. There results from this a magnified potential difference between the output terminals In the arran' ement illustrated in Fig. 5 showing the utllization of the falling voltage-current characteristic of the device to counteract a resistance, the reduced current effect in the A anode circuit enables the effective resistance in a circuitto be reduced e. g. by inserting it between the terminals K, L in the A. anode circuit. An oscillatory circuit 0 may be connected between these terminals as indicated for the pur ose of producing continuous oscillations. scillations produced in this circuit arise by virtue of the falling voltage-current characteristic of the A anode circuit. Both in this case and in the amplifying arrangement illustrated in Fig. 3, the change of potential due to change of current in the resistance It may be amplified before being applied to the grid G.

It will be obvious that the indicating device I may be included in the B anode cir- At the same time the A anode cuit in the several arrangements hereinbefore described, since a variation in the A anode current is always accompanied by an opposite variation in the B anode current. Also the B anode circuit may be used as the output circuit in arrangements using the negatron.

In all uses of the negatron such as herein described the diversion effect may be adjusted by altering the strength of the filament current, an increase of which diminishes the extent to which current is diverted from one anode to another.

While some methods of using the negatron have been suggested, many additional applications of the device will occur to those skilled in the art.

Having thus described the nature of the said invention and the best means I know of carrying the same into practical effect, I claim I 1. The combination with a thermionic device having a plurality of anodes, a cathode, and a control electrode cooperating with said cathode, and with one of said anodes, of a circuit containing inductance and capacity connected between the cathode and another of the anodes, means maintaining a difference of potential between said last named anode and the control electrode and means maintaining potential differences between both said anodes and the cathode.

2. A thermionic device having a 'cathode, a plurality of anodes, and a control electrode in the electron path between the cathode and one of said anodes, means for causin electrons to flow from the cathode to sai anodes and means whereby some of the electrons normally passing from the cathode to one of the anodes are diverted to another anode when the potential of the former anode with respect to the cathode is increased.

3. The combination in a vacuum tube of a cathode, and two anodes, means for causing a flow of electrons from said ca'thode to both of said anodes, and means for varying the potential of one of said anodes with respect to the cathode, and means for causing the flow of electrons to said anode to be increasingly diverted to the other as the said potential of the first named anode is increased.

4. In a vacuum tube having a cathode and two anodes so placed that space currents may pass between said cathode and both said anodes in separate paths, having no portion in common, the method of controlling the current in one of said paths which comprises diverting electrons therefrom to the other path by and in proportion to po\ tential difierence increases set up at the extremities of said first named path.

5. In a vacuum tube having a cathode and a plurality of anodes the method of controlling a space current between the cathode ioa and one of said anodes which comprises settin up another space current between said cat ode and another of said anodes, maintaining the operating conditions such that 5 the sum of said space currents remains substantially constant, and causing said second sfiace current tova in the inverse sense to t e variation desire in the first current.

6. A vacuum tube having a cathode and 1 two anodes arranged to provide two indenouns? gndent electron paths,

ing of substantially lower normal impedance than the other a control electrode inter ed inthe said lower-im ance path, an means for maintaining sai tive with respectto the cathode.

In testimony whereof I have signedmy name to this specification.

JOHN SCOTT-TAGGART;

one of said paths anodes posi- 

